Centrifugal blower



Jan. 23, 1968 R. e. HAJEC ETAL 3,365,122

CENTRIFUGAL BLOWER Filed Feb. 2, 1966 4 Sheets-Sheet '1 Fla INVENTORS. RICHARD G. HAJEC a WILLIAM A. SEABURY III BY their ATTORNEYS Jan. 23, 1968 R HAJE ETAL 3,365,122

GENTRIFUGAL BLOWER Filed Feb. 2, 1966 j 4 Sheets-Sheet 2 1 3 2 LL! I u. 0

0U) 2 7 f- 0 1 1 I 1 I g 0 I I00 200 300 400 500 600 F 5 AIR VOLUME CFM F 500 1 I l I I 1 I i INVENTORS. 3 RICHARD s. HAJEC a m; 0 WILLIAM A. SEABURY m :3 I00 J B their ATTORNEYS Jan. 23, 1968 R. e. HAJEC ETAL'.

CENTRIFUGAL BLOWER 4 Sheets-Sheet 3 Filed Feb. 2. 1966 5 w TC NE EJ M e D R A H m R 8: WILLIAM A. SEABURY ll l ATTORNEYS BY HG WZ @%W @MM their Jan. 23, 196 8 R HAJEC ETAL 3,365,122

CENTRIFUGAL BLOWER Filed Feb. 2, 1966 4 Sheets-Sheet 4 INVENTORS. RICHARD G. HAJEC & WILLIAM A. SEABURY III their ATTORNEYS I United States Patent 3,365,122 CENTREFUGAL BLUWER Richard G. Hajec, Woodstock, and William A. Seahury III, Ulster Park, N.Y., assignors to Rotron Manufacturing Company, Inc., Woodstock, N.Y., a corporation of New York Filed Feb. 2, 1966, Ser. No. 524,507 14 Claims. (Cl. 230-117) ABSTRACT OF THE DISCLOSURE A blower including a casing and an impeller providing a central axial intake and a centrifugal discharge, in which the casing defines a convolute flow chamber having a circumferential inlet passage adjacent the impeller periphery to receive fluid discharging therefrom and communicating with the chamber interior, the chamber having an elliptical cross-section which is generally symmetric about its own axes in radial planes passing through the convolute axis, the major axis of the cross-section being parallel to the convolute axis at a small radius end of the chamber and normal to the convolute axis at a large radius end of the chamber. The cross-section of the casing progressively shifts in a direction parallel to the convolute axis of the chamber and away from the axial intake as the radius of convolution increases. The impeller is driven by a motor secured to a housing which is relatively rotatable with respect to the casing and is located opposite the axial intake so that the motor is at least partially surrounded by the convolute chamber.

This invention relates to centrifugal fans or blowers, and more particularly to centrifugal blowers often used in applications requiring a blower of minimum weight and dimension and capableof optimum flow delivery.

In recent years, with the advent of electronic miniaturization, the need for a small, efiicient cooling fan has become recognized. As is well known, electronic circuitry, and in particular semiconductor components, must be maintained within certain temperature limits for satisfactory performance. The physical contraction of component size and the use of microcircuitry have resulted in higher package density, Le, a greater number of electronic components within a given volume. To maintain the equipment within prescribed temperature limits, cooling air is usually circulated about the components. For this purpose, centrifugal type fans are often preferred because they are well adapted to circulation of the coolant against substantial pressure drops. High package density has necessitated, however, the use of fans capable of delivering air flow at increased initial pressures to sustain adequate cooling air flow throughout the cycle. As a further requirement, it is highly desirable that the fan or blower be of minimum dimension and weight in keeping with the desirability and advantages of compactness.

It is a familiar fact that the performance of a centrifugal fan is largely dependent on the size of a rotating impeller. It is evident, therefore, that in order to achieve a reduction in the overall size of the blower, without a reduction in flow rate capacity, the fan or blower must possess superior efficiency. An increase in efiiciency also allows the use of a smaller motor to drive the blower impeller.

It is one object of this invention, therefore, to provide a centrifugal fan having improved efficiency over other fans of this type.

Another object of the invention is to provide a highly efiicient centrifugal blower whose flow performance is optimum for its size and-weight.

Still another object of this invention is to provide a centrifugal fan having smaller dimensions than those of known centrifugal fans having comparable performance.

These and other objects of the invention are attained by surrounding the blower impeller with a casing having a convolute air flow chamber whose cross-sectional area is generally elliptical in shape and increases in the direction of impeller rotation. The major axis of the cross-section ellipse is parallel to the rotary axis of the impeller at the small area end of the convolute and perpendicular to the rotary axis at the large area blower outlet. This arrangement enables optimum cross-sectional areas to be provided in the air flow chamber for the volume occupied by the casing. The overall dimension of the blower assembly is further reduced by partially integrating the motor into the blower casing. This also increases overall efficiency by subjecting the motor to forced air cooling from the main airstream. Additional cooling is achieved by providing a coupling between the motor rotor and the impeller formed of a material having a high thermal conductivity, thereby conducting motor heat to the impeller which acts as a heat sink.

For a better understanding of the invention, reference may be made to the following detailed description of an exemplary embodiment, and to the accompanying drawings wherein:

FIGURE 1 is a front elevation of a blower in accordance with the invention partially in cross-section;

FIGURE 2 is a partially cut-away side elevation of the blower of FIGURE 1;

FIGURE 3 is an elevation of the other side of the FIGURE 1 blower;

FIGURES 4A-4D are a series of cross-sections through the blower casing, taken generally along the lines A-A, BB, CC and D-D of FIGURE 3, respectively; and

FIGURE 5 is a performance graph for a typical blower constructed in accordance with the invention.

As previously mentioned, air flow delivery of a centrifugal blower is primarily proportional to the size of the impeller. The amount by which the radial and lateral or axial dimensions of the impeller may be decreased for overall compactness, therefore, is limited by the required size of the impeller and the fan efiiciency. In conventional blowers, the overall radial dimension cannot be lessened without detracting from its efi'iciency or air flow delivery. In accordance with the invention, however, the radial dimension of the blower is decreased by incorporating a specially designed blower casing with a chamber of elliptical cross-section. Weight and dimension of the blower are further lessened by using a smaller motor which is permitted by virtue of the increased cooling achieved by the construction. A further decrease in overall package size is made possible by partially incorporating the motor into the casing. It is, therefore, a combination of the foregoing features (i.e., small size, high capacity, and light weight) for optimum performance that further enables this blower to attain the objects it was designed to meet.

Referring now to FIGURES 1 and 2, a blower in accordance with the invention includes an impeller 10 driven by the motor 12 for rotation within a housing, or casing 14. This casing 14, which may be fabricated from lightweight polyester resin, is formed with a convolute air chamber 15 of generally elliptical cross-section. As indicated in FIGURE 1, the interior circumferential portion 17 of the chamber is open to receive the discharge from the periphery of the impeller 10. Rotation of the impeller 10 draws air into an inlet opening or duct 16 at the side of the casing 14, the edge 16a of which is contoured to the intake flow, and the blades 10a convert the axial intake to a centrifugal discharge into the open interior portion 17 of the convolute chamber 15. In this regard, it will be observed that the impeller forms a continuous curved passage from the axial intake 16 to the circumferential inlet 17 so that all intake flow to the cornpressor is through the impeller.

As best seen in FIGURE 2, the convolute chamber 15 includes a throat or cutoff 18 at the junction of the diffuser section 19 and the convolute portion of the casing 14. The lower edge 18a (i.e., the edge toward the direction of impeller rotation) of the cutoff is angularly disposed relative to the impeller blades a. As shown in FIGURE 1, the edge 18a bridges a pair of consecutive blades 19a, thereby eliminating pulsation and noise which would otherwise be generated by the departure of the air trapped between consecutive blades 10a as they rotate past the throat.

From the inlet end of the chamber 15, immediately below the throat 19 (FIGURE 2), the cross-sectional area and radius of convolution of the chamber gradually increase (in the direction of impeller rotation). At the same time, as best observed from FIGURES 4A-4D, the ratio of the dimension a to the dimension 20b of the elliptical cross-section of the chamber gradually increases until at the outlet of the chamber to diffuser section 19, this ratio is greater than 1. That is, the axis of the elliptical cross-section parallel to the axis of the motor 12, which is the major axis at the small area portions of the convolute (FIGURE 4A), gradually transforms to the minor axis at the outlet of the chamber (FIGURES l and 4D), the major axis there-at being in a plane perpendicular to the motor axis.

Another distinctive feature of the casing 14 is the gradual shift of the cross-section of the chamber in the direction of the convolute axis as the radius of convolution changes. Specifically, the convolute chamber progressively shifts away from the axial intake 16 and toward the motor 12 as the radius of convolution increases.

Progressing further along the curved length of the chamber 15 from the small to large convolute radius end, the normal (vertical) chamber axis 20a continues to move in a direction parallel to the other axis 20b and parallel to the convolute axis so that the chamber crosssection at the diffuser 19 is markedly farther away from the intake 16 and closer to the motor 12. As seen in FIGURE 4A, a section through the chamber near the small radius end of the convolute, the cross-section is located to be nearer the axial intake 16, with the normal axis 20a located near a corner of the blade 10a closest to the axial intake. In FIGURES 4B and 4C taken through the chamber 15 at greater radii of convolution, the axis 20a is located at an intermediate axial position approaching the middle of the impeller blade tips. Finally, prior to reaching the outlet in the diffuser 19, the axis 20a has shifted to the other side of the center of the blade tips to be at a position away from the intake 16 and closest to the motor 12. The inlet 17, on the other hand, shifts, relative to the chamber cross-section, toward the axial intake 16 as the radius of convolution increases. Again, this can be seen quickly by comparing the location of the axis 200 relative to the circumferential inlet 17 and blades 10a in FIGURES 4A4C and FIGURE 1. In this manner, the centerline of the flow passage in the casing is caused to shift axially relative to the impeller blades to induce the desired fluid motion while at the same time presenting to the incoming fluid a smooth flow passage transition and preserving the axial compactness of the unit.

At all points along the chamber 15, the cross-sectional area is such as to provide optimum air flow characteristics. As is readily apparent from the drawings, the foregoing configuration combines optimum air fiow characteristics with minimum axial and radial dimensions.

Referring in particular to FIGURE 1, the motor 12 is illustrated schematically, showing its position relative to the blower. The motor includes a stator 21 and a rotor 22 journaled on the shaft 23 by the bearings 24 and 25. In accordance with the invention, the motor stator windings 21a and portions of the rotor 22 are exposed to the moving air circulated by the rotating impeller 10 within the casing 14. The partial incorporation of the motor 12 into the blower housing 14 serves two purposes. First, a considerable reduction in the axial length of the blower is realized; and second, the transfer of heat away from the windings 21a and the rotor 22 by the cooling elfect of the circulatory air permits the employment of a smaller motor. This latter result, in turn, further diminishes the axial length of the blower assembly and the power requirements.

Connecting the impeller 14 t the rotor 22 is a generally cylindrical combined rotor end ring and hub 27 of aluminum or other suitable material having a high thermal conductivity. The hub 27 is a continuation of the rotor and has a substantial surface 27b in thermal contact with the metal parts of the impeller 10. This construction provides ready transfer of heat from the rotor 22 to the impeller 1%, which because of the large air flow through it, acts as a heat sink.

Supporting the motor shaft 23 and enclosing the outboard or left-hand end of the motor 12 is a motor housing 30 having a flange portion 31 adjacent its inner end. The flange 31 is provided with a circumferential groove 32 in its face 33 near its outer perimeter for accepting a cylindrical projection 34 formed on the blower casing 14. This permits the casing 14 to be slidably rotated with respect to the motor housing 30. If the blower is to be supported by fastening the motor housing 30 to an external support (not shown), as, for example, by bolts inserted through the support and the tapped holes 35 at the bottom of the motor housing 30, the casing 14 may be rotated relative to the external support so that the delivered air blast can be directionally changed over 360.

The housing 30 and the blower casing 14 may be fastened together by means of the arrangement described in the copending application Ser. No. 524,540, filed Feb. 2, 1966, by William A. Seabury III for Adjustable Clamp, and assigned to the present assignee. Briefly, the clamp includes a plurality of clamping blocks 40 which have an inclined surface 40a at one end adapted for sliding motion along plane surfaces formed on a like plurality of ribs 42 radially disposed on the motor housing 30. A tightening screw 44 inserted through a slot 45 in the motor housing engages each clamping block 40. VVnen the screws are tightened, the blocks 40 are drawn toward the screw head, bearing against the inclined plane of the rib 42 and the shoulder 34 to secure the casing to the motor housing. A relatively slight loosening of the screws enables the two members to be separated without disassembling the clamp.

The flange 31 on the motor casing 30 may also be formed with an axial extension 31a to provide a circumferential cavity 50 extending around the motor 12. Such a cavity, which does not increase the overall radial dimension of the blower, may be used to house electric-a1 elements, such as the starting capacitor 51 illustrated in an upper portion of the cavity 50, switches, overload relays, etc. A suitable press-fitted ring 52 may be provided to seal off the cavity 50.

An appreciation of the characteristics of a fan according to the invention may be gained from an examination of the performance graph of FIGURE 5, obtained from a fan whose dimensions measure less than 11 inches by 12 inches by 7 /2 inches deep, and weighing 14 pounds. As observed from the graph, the blower of the above dimensions can deliver in excess of 300 cubic feet per minute at a static pressure of 3 inches water. Thus, the invention provides a centrifugal blower which achieves superior performance with an optimum balance of size and weight.

As indicated above, the entire unit may be mounted on a supporting surface or bracket with screws engaged in the tapped holes 36 in the housing portion 31a. Alternatively, the unit may be secured against a plate or wall having a suitable opening for the discharge end of the diffuser portion 19, the flange 48 thereat being provided with holes 48a for suitable fasteners. Although not shown, the outer or left-hand end of the motor housing may be drilled and tapped to accept threaded fasteners for mounting against a panel or bracket.

The specific embodiments described herein are illustrative only and any modifications and variations, both in form and detail, may be made therein within the skill of the art. All such modifications and variations, therefore, are intended to be included within the spirit and scope of the appended claims.

We claim:

1. A casing for a centrifugal blower, said casing formed with a convolute flow chamber of generally elliptical crosssection and having an interior circumferential inlet passage and an outlet for fluid carried therethrough, the ratio of the minor axis dimension to the major axis dimension of said cross-section progressively increasing from a small radius end of the convolute chamber to near the outlet thereof, the major axis being generally parallel to the convolute axis at the small radius end and generally normal to said convolute axis at the outlet, the cross-section of the convolute chamber being substantially symmetric about both the major and minor axes throughout the convolute length thereof.

2. A casing adapted to surround the impeller of a centrifugal blower, said casing formed with a convolute flow chamber having an interior circumferential inlet passage adjacent the periphery of the impeller and an outlet for the fluid carried therethrough, the radius of convolution of said chamber about its axis increasing in the direction of rotation of the impeller, said chamber having a generally elliptical cross-section whose major axis is approximately parallel to said axis at the shortest said radius and generally perpendicular to said axis at the longest said radius.

3. A casing as defined in claim 2 wherein the crosssectional area of said chamber progressively increases as the radius of convolution increases.

4. A centrifugal blower, comprising a motor, a rotary impeller driven by the motor, and a casing surrounding said impeller and formed wih a convolute flow chamber having an interior circumferential inlet passage adjacent the periphery of the impeller and an outlet for the air carried therethrough, said chamber further having a generally elliptical cross-section, the radius of convolution and cross-sectional area of said chamber progressively increasing in the direction of air flow therethrough and overlying said motor, said motor being mounted onto the casing to be partially surrounded by the chamber, the circumferential inlet communicating with the interior of the casing to expose the motor to airflow adjacent an interior side of said impeller to cool said motor.

5. A centrifugal blower in accordance with claim 4 wherein said motor includes a rotor having a metal core member, and further comprising means connecting said impeller in driven relation to the rotor, said means constructed from a heat-conductive material and contacting the impeller and a substantial portion of an end of said core member for transferring heat away from the motor to the impeller.

6. A centrifugal blower in accordance with claim 4, further comprising a motor housing enclosing a portion of and supporting the motor for coaxial mounting to said casing.

7. A centrifugal blower as defined in claim 6 wherein said motor housing includes means for mounting the blower to an external support and is slidably rotatable with respect to said casing to chan e the direction of fluid outlet flow from the chamber relative to the housing.

8. A casing for a blower having an impeller providing a centrifugal discharge, said casing formed with a convolute flow chamber having an outlet and an interior circumferential inlet passage surrounding and adjacent to the periphery of the impeller, said casing including a diffuser section at the outlet thereof, the radius of convolution of said chamber about its axis increasing in the direction of impeller rotation, said chamber having a generally elliptical cross-section whose major axis is approximately parallel to said axis in the portion of the casing adjacent the impeller and approximately perpendicular to said axis in the diffuser section.

9. A blower as set forth in claim 4, in which the crossseotion of the chamber progressively shifts parallel to the convolute axis away from the axial intake and toward said motor as the radius of convolution increases.

10. A casing as defined in claim 8, in which the crosssection of the casing gradually moves in a direction parallel to the convolute axis, as the radius of convolution increases, away from the axial intake.

11. A casing as set forth in claim 10, in which the circumferential inlet gradually shifts axially of the convolute toward the axial intake as the radius of convolution increases.

12. A blower comprising a casing, an impeller including blades providing a central axial intake and a centrifugal discharge, and a motor mounted to the casing opposite the axial intake to rotate the impeller, the casing defining a convolute flow chamber having a circumferential inlet passage adjacent the impeller periphery to receive the centrifugal discharge therefrom, the cross-section of the casing being everywhere substantially symmetric about its axes normal and parallel to the convolute axis and progressively increasing from a small radius end of the chamber to a large radius end, the cross-section of the chamber progressively shifting in a direction parallel to the impeller axis away from the axial intake and toward the motor as the radius of convolution increases.

13. A blower comprising a casing and an impeller providing a central axial intake and a centrifugal discharge, the casing defining a convolute flow chamber having an outlet and an interior circumferential passage adjacent the impeller periphery to receive the fluid discharging therefrom, the radius of convolution of the chamber increasing about its axis in the direction of impeller rotation, the chamber having an elliptical cross-section whose major axis is parallel to the convolute axis at the shortest said radius and is normal to said axis at the largest said radius, the casing forming with the impeller a continuous curved inlet duct to provide essentially a single continuous inlet flow passage for converting axial intake flow to centrifugal discharge flow.

14. A blower as defined in claim 13, in which the axis of the ellipse normal to convolute axis gradually moves in a direction parallel to the convolute axis and away from the axial intake as the radius of convolution increases, the chamber cross-section and impeller everywhere intersecting a plane normal to the axis of convolution.

References Cited UNITED STATES PATENTS 2,311,024 2/ 1943 Buchi.

2,486,731 11/1949 Buchi.

2,641,191 6/1953 Buchi.

FOREIGN PATENTS 1,003,749 3/1952 France.

HENRY F. RADUAZO, Primary Examiner. 

